Numerous conventional methods exist for sustaining microorganism culture. However, these methods suffer from numerous inefficiencies. There remains a need for additional more effective methods for sustaining microorganism cultures in the absence of various substrates in a syngas fermentation process.
Three strains of acetogens (Drake, 1994) have been described for use in the production of liquid fuels from syngas: Butyribacterium methylotrophicum (Grethlein et al., 1990; Jain et al., 1994b); Clostridium autoethanogenum (Abrini et al., 1994); Clostridium ljungdahlii (Arora et al, 1995; Barik et al., 1988; Barik et al. 1990; and Tanner et al., 1993). Of these, Clostridium ljungdahlii and Clostridium autoethanogenum are known to convert CO to ethanol.
U.S. Pat. No. 5,173,429 to Gaddy et al. discloses Clostridium ljungdahlii ATCC No. 49587, an anaerobic microorganism that produces ethanol and acetate from CO and H.sub.2O and/or CO.sub.2 and H.sub.2 in synthesis gas.
U.S. Pat. No. 5,192,673 to Jain et al. discloses a mutant strain of Clostridium acetobytylicum and a process for making butanol with the strain.
U.S. Pat. No. 5,593,886 to Gaddy et al. discloses Clostridium ljungdahlii ATCC No. 55380. This microorganism can anaerobically produce acetate and ethanol using waste gas (e.g. carbon black waste gas) as a substrate.
U.S. Pat. No. 5,807,722 to Gaddy et al. discloses a method and apparatus for converting waste gases into useful products such as organic acids and alcohols using anaerobic bacteria, such as Clostridium ljungdahlii ATCC No. 55380.
U.S. Pat. No. 6,136,577 to Gaddy et al. discloses a method and apparatus for converting waste gases into useful products such as organic acids and alcohols (particularly ethanol) using anaerobic bacteria, such as Clostridium ljungdahlii ATCC Nos. 55988 and 55989.
U.S. Pat. No. 6,136,577 to Gaddy et al. discloses a method and apparatus for converting waste gases into useful products such as organic acids and alcohols (particularly acetic acid) using anaerobic strains of Clostridium Ijungdahlii.
U.S. Pat. No. 6,753,170 to Gaddy et al. discloses an anaerobic microbial fermentation process for the production of acetic acid.
U.S. Pat. No. 7,285,402 to Gaddy et al. discloses an anaerobic microbial fermentation process for the production of alcohol.
Other strains of aceotgens have also been described for use in the production of liquid fuels from synthesis gas, e.g.: Butyribacterium methylotrophicum (Grethlein et al., 1990, Appl. Biochem. Biotech. 24/24:875-884); and Clostridium autoethanogenum (Abrini et al., 1994, Arch. Microbiol. 161:345-351).
There remains a need in the art in preserving culture in syngas fermenation process in decreased concentration or absence of various substrates. There is a need to sustain cultures in the event of various interruptions in industrial process of alcohol production. Particularly, there remains a need to sustain microorganism culture in the event of decreased: CO, H2, or CO and H2 in various concentrations.